[dpoltzer]

1970 T/A: I have a Pontiac am-fm (red dot) stereo from the early 70s in my car. I have a 1970 factory original radio harness installed as well. I have installed two speakers in the trunk compartment that are aftermarket. My question is: how do I get these two rear speakers wired in to the rear speaker connector that has one blue and one black wire in it. Also, this car came from the factory with an am radio with the one front speaker that is fed by the green wire. I do not have a front speaker in the car now or intend to add one. do I need to use the green wire at all in the wiring or just cap it off. Thanks.

[fbody_mike]

You could run the green wire to the rear for the second speaker. The negative side of the speaker is just connected to ground as the chassis ground of the radio is also the speaker's negative side.
BUT, do not connect an aftermarket 4 ohm speaker to this radio. It will eventually kill the output transistor if you do. These radios require a 8 or 10 ohm speaker and the DC resistance is also important as this helps bias that transistor.

[fbody_mike]

Also if you run the green wire to the rear, I'd just tap off the black wire of the blue/black pair to supply the negative of the right speaker.
Again, make sure you have the correct 6x9 speakers. Check out http://www.turnswitch.com/speakers.htm

[Formulabruce]

Ok, the rear "one wire" was not for stereo radios, only mono, and required a condenser on the hot side of coil.
As Mike stated factory radios need 8 to 10 ohm ratings.
As I recall the Stereo radio does use a common ground wire, but separate left and right. The Blue was rear (or right) and green was front (left). So to add to what Mike said, run a negative wire for each and the the green and blue for + for each side. Run a 18 gauge for stock radio.
I used Turnswitch as Mike mentioned and very happy with the results and can run a modern speaker(s).
Keep in mind your full size spare will not fit with a right rear speaker if in its correct location.
Also the factory underside speaker covers (Ames has them) make a huge difference in sound quality.

[fbody_mike]

Yup, I ran for a while without the speaker cover. I had a thread on here where I asked if it was worth it, the consensus was yes. I was surprised by how it improved the speaker. I also run a factory 8-track and some of my carts still sound really good, like my Boston one. Sounds pretty good for a 50 year old stereo with "new" speakers.